Lubricating grease thickened with a sodium or lithium soap and indigo



United States Patent LUBRICATING GREASE THICKENED WITH A SODIUM 0RLITHIUM SOAP AND INDIGO John P. Dilworth, Fishkill, and James R. Roach,Beacon, N. Y., assignors to The Texas Company, New York, N. Y., acorporation of Delaware No Drawing. Application April 14, 1954,

Serial No. 423,240

12 Claims. (Cl. 252-421) This invention relates to lubricating greaseswherein indigo and a soap are employed in combination as thickeningagents.

We have found that very superior lubricating greases are obtained byemploying indigo in finely divided form as a thickening agent inconjunction with certain fatty acid soaps. The greases thus produced arecharacterized by very outstanding high temperature performanceproperties, which are generally far superior to those obtainable byemploying other finely divided solid thickening agents of the prior arteither as the sole thickening agent or in combination with fatty acidsoaps.

The lubricating greases of our invention comprise an oleaginous liquidlubricating base thickened to a grease consistency with at least asubstantial proportion of indigo in finely divided form, suitably in theform of particles not more than about one micron in diameter, and atleast a substantial proportion of a sodium or lithium soap of arelatively low molecular weight soap-forming fatty acid. The compositionmay suitably comprise about 5 to 20 percent by weight based on theweight of the composition of indigo in finely divided form and about 5to 20 percent by weight based on the weight of the composition of a soapof the above type, the two materials being present in amounts sufficientto thicken the composition to a grease consistency by their combinedeffect. The indigo and soap are preferably employed in a proportion offrom about 2 to l to about 1 to 2 by weight.

The soaps which may be employed in these compositions are sodium andlithium soaps of fatty acids having about 12 to 16 carbon atoms permolecule, such as for example sodium laurate, lithium laurate, sodiummyristate, lithium myristate, sodium palmitate, etc., as well asmixtures of such low molecular weight fatty acid soaps. The preferredsoaps of this character are sodium and lithium soaps of low molecularweight fatty acids con taining at least a predominant proportion ofmyristic acid. Also, it is to be understood that the sodium and lithiumsoaps are not regarded as entirely equivalent for this purpose, and ingeneral the sodium soaps are preferred. However, both the sodium andlithium soaps of the low molecular weight fatty acids, and particularlythose of myristic acid, produce a very pronounced synergistic effect incombination with indigo upon the high temperature performance propertiesof the grease, and are therefore both included in the purview of thisinvention.

The lubricating oil base may be any suitable oil of mineral, vegetable,animal or synthetic origin, such as have been employed heretofore inlubricating greases. With particular advantage, where a wide temperaturerange grease is desired, the oil base may comprise at least asubstantial proportion of a high molecular weight polyester oflubricating characteristics.

Additives of the usual types may be employed, such as oxidationinhibitors, corrosion inhibitors, tackiness agents, extreme pressureagents, and so forth. An oxida- 2,791,560 Patented May 7, 1957 tioninhibitor is preferably employed, which may suitably be an inhibitor ofthe amine type, such as diphenylamine, a-naphthylamine, b-naphthylamine,p-phenylene diamine and N,N diphenyl p-phenylene diamine. A compound ofthis type may be present in amounts of from about 0.05 percent to about5 percent by weight based on' the weight of the composition. Also,additional thickening agents may be present in minor amounts, such asother soaps and other finely divided solids.

The preparation of these greases may be carried out by any convenientmethod, such as by adding the soap and the indigo either separately ortogether during the grease making process, or by separately forming agrease containing a sodium or lithium soap of a low molecular weightfatty acid as the chief thickening agent and a grease containingindigoin finely divided form as the chief thickening agent ,and thenmixing the two. The soap is preferably prepared by saponifying a mixtureof low molecular weight fatty acids comprising at least 70 percent, andpreferably at least 90 percent of myristic acid and the glycerides ofsuch acids with an aqueous solution of sodium or lithium hydroxide inthe presence of a small amount of mineral lubricating oil. A smallexcess of sodium hydroxide may be employed in this saponification; forexample, the finished grease may con tain about 0.020.2 percent of freealkali (calculated as sodium or lithium hydroxide). However, this is notan essential condition, and the grease may be neutral or even slightlyacid if desired. 7

As a preferred embodiment of this invention, lubricating greases ofoutstandingly superior properties over a wide temperature range areobtained by employing both indigo in finely, divided form and a sodiumor lithium soap of a low molecular weight fatty acid as described aboveas thickening agents in a high molecular. weight polyester of the typedisclosed by R. T. Sanderson in U. S. 2,628,974, obtained by reacting adibasic aliphatic acid with a glycol and end blocking the reactionproduct with a monohydric aliphatic alcohol or a'monocarboxylicaliphatic acid. Particularly suitable polyesters of this character areproducts obtained by reacting a monoor poly-alkylene glycol with adicarboxylic acid and a monohydric alcohol, represented by the formulawherein R is an aliphatic group or an aliphatic other group containingfrom 4 to 12 carbon atoms, R1 is an aliphatic group containing from 1 to12 carbon atoms, R2 is an aliphatic group containing from 1 to 12 carbonatoms, and x is an integer from 1 to 5. Preferably, R is an aliphaticgroup or an aliphatic ether group containing from 6 to 12 carbon atomsin branched chain arrangement, R1 is an alkylene group containing 7 to 8carbon atoms, R2 is an alkyl group containing from 4 to 9 carbon atomsin branched chain arrangement and x is 1 or 2. An ester of this typepreferably comprises from about 20 percent up to percent of the oilcomponent of the grease, the remainder being a mineral oil or other oilof a different type. The composition preferably contains also about0.1-8 percent by weight of N,N' diphenyl para-phenylene diamine andabout 05-15 percent by weight of tricresyl phosphate.

Greases of the above type, wherein both indigo and a sodium or lithiumsoap of low molecular weight fatty acids are employed as thickeningagents in a high molecular weight polyester, have very exceptional hightemperature properties, required for the long-time lubrication ofbearings at temperatures as high as 400 F., in addition to excellent lowtemperature properties down to --60 F.

The following examples are given in order to more fully disclose theinvention.

Example I is illustrative of attempts to obtain high temperature greasescmploying' Agrease was prepared having the following composition byweight:

ie'rcent Indigo 3'510 Diphenyl-p-phenylenediamine 1.0 Tricresylphosphate; 3.0 Mineral -oil-. 4. 3 Synthetic ester j 516.7

The synthetic ester was obtained by .reacti-ngtogether sebacic acid,2-ethylhexane-L 3-idio1 and EZ-ethylhexanol inabouta.2:;1:2'ratio,respectively, consisted p're dominantly .of the compound .(iso-CsHrr)(CH2) a-COOiSo- I aHisoOQ-{lcHzhcoO (iso CaI-Iri).

The mineral oil was a refined parafliuic distillate oil liavin'g-a'nSUSviscosity at lOOF. of 330. I

The indigo was the .dye ,grade product-ohtainedfrom National AnilineDivision or Allied Chemicaland Dye Corporation. This was inlthe form ofa powder having an average particle size of about .0.1 micron diameter,arid a measured "surface area of about to '50 square meters per gram.

The .grease was prepared by mixing the indigo and the oleaginous 'hasetogether by means of an electric stirrer until a smooth paste wasformed. The inhibitors were then added and the grease was finished bymilling with two-passes through aPremier Colloid Mill at 0.002 and0.0015 inch clearance.

A soft purple grease was obtained having a dropping point of 500+ F. andan ASTM worked penetration at 77F. of 3 71.

EXAMPLE 2 :A igrease was prepared having the following compositionbyweight:

Percent Indigo 10.0 Sodiumu'nyristate; ..J 10.0Diphen'yl-p-phnylcnediamine lfJO Tricresyl phosphate 3;0 lvlirteial oilna 510 Synthetic ester 7150 With the exception inf the sodium 'myristateall of the materials employed in the preparation of .thisgrease were thesame as those ie-mployedin the :grease of Example 1'.

The;grease was prepared in the following manner: A soap -base' wasformed by saponifying a commercial myristic ;acid,'=having asaponification number of 250 and a titer, C. of 42.16, with'thetheoretical amount of so dium hydroxide in the presence of the minerallubricating oil included in the grease, and then dehydrating" for 1%hours at 300-320 F. The dry indigo powder'was thcn added to :theconcentrated soap solution and the temperature maintained at 300-3202-F.for 1 hour longer-with continuous stirring. The-synthetic ester wastheri'added gradually while"the grease mixture was cooled down' to 22091 Nearthe end ot-the ester addition the inhibito'rs were-added.

Arshort'fiber :bluei grease was obtained havingaa dropping Zpoint of 4021F., aud an 'ASTM worked penetration at 77 of 2 3.6.

In -a-numher of other preparations ofpg'reases: of the aboveqtype whichwere earried out-employing'ithe ;1-:l' indigo-sodium myristate mixture,the amount-:ofwthiebening agent required was from about percent for aNo. '1 "grade grease up to about percent'for aNo. 3 grade grease, as inExample 2. In comparison with these yields, a grease having an ASTMworked penetration at 77 F. of 274 (No. 2 grade) was obtained from 18.4percent of sodium myristate in atypical preparation employing sodiummyristate as the sole thickening agent.

A Mixtures of indigo and sodium myristate in proportions as high as 1:1by weight are thus fully equivalent to sodium'myristate alone inthickening powerin these greases, the effectiveness of indigo asathickening agent in combination with sodium myristate being in markedcontrast to its deficiency in thiclreningpowerwhen employed as the solethickeningagent, as shown by Example 1. The use of higher proportions ofindigo in the mixtures results in decreased yields, although proportionsas high as 2:1 may be employed without decreasing the yieldsexcessively. For example, a grease having .an AS'I-M worked penetrationat 77 F. of 373 v(No. .0 grade) was prepared from 22.5 percent of a 2:1indigo-sodium myristate mixture.

EXAMPLES A;gr,ease was prepared having the {following composition byweight:

Percent Lithium myris e 8.6 Diphenyl-p phenylenediamine 0.9 Triscresylphosphate 2.7 Free alkali as LiOH) 0.1 Mineral oil 8.5 Synthetic ester70.0

hydroxide was employed in the saponification in placeof sodiumhydroxide, with a slight excess of lithium hydroxide over the amounttheoretically required. Following the saponification the mixture washeated to 425 F. and cooled immediately to 300F. 'The indigo was thenadded and the temperature maintained at'300" F, for 1 hour longer withcontinuous stirring. The addition of the synthetic ester and of theinhibitors was then carried'out'as described in Example 1. Theproductfinished bycirculating it-for l5 n-iinutesinaManton Gaulin Homogenizerat 4000nnd 5000 poundspressure.

'A s o'ft smooth blue; grease -wasobtained "having a dropping-point 'of462" 'F. and an 'ASTM'worked penetration at-77 'F. 015357.

' EXAMPLE 4 A grease was preparedhaving'the following composition byweight:

Percent Indigo 10.0 50 Sodium:myristate 10.0 Diphenyhpphenylenediamine1.0 Tricresyl phosphate 3.0 Mineral "oil- 5.0

point iii-58.8 Rand 311" ASTM :worked,;pnetration of- Ditridecylazelate,71.0

Table I shows the high temperature performance prop erties of thegreases of the above examples (greases Nos. 1, 2, 3 and 4,respectively), together with comparative data obtained upon a greasethickened with sodium myristate alone and upon greases containing carbonblack as a thickening agent. The latter are included as representativeof the other solid thickened greases of the prior art. These greasescontained the same ester base and inhibitors as greases Nos. 1, 2 and 3,greases Nos. 5 and 7 containing 10 percent and 4 percent, respectively,of the mineral lubricating oil employed in the greases of the examplesin admixture with the ester, and grease No. 6 containing the ester asthe sole oleaginous component.

Table I HIGH TEMPERATURE PERFORMANCE TEST The high temperatureperformance test of the foregoing table is a test for determining theperformance characteristics of greases in anti-friction bearings atelevated temperatures and high rotative speeds. The test unit consistsessentially of a steel spindle supported on ball hearings in anelectrically heated housing and driven by an electric motor connectedinto an electric circuit containing a low amperage fuse 0.1 ampere belowthat required for full load running. The bearings are Norma- HofifmanABEC No. 3 grade, and are mounted on a spindle approximately 5% inchesapart. A thrust load of 17.5 pounds is applied to the bearings. Onebearing is used for test purposes and the second bearing, which is notheated, is used as a guide bearing. The test consists of operating thetest bearing for twenty-four hours at 10,000 R. P. M. and at atemperature of from 250 F. to 450 F. followed by a shut down and coolingperiod of two hours, and repeating this cycle until the lubricant fails,which is indicated by rupture of the low amperage fuse in the motorcircuit. In carrying out the test at 400 F. or above, Marlin Rockwellspecial heat treated high speed tool steel bearings with silver platedbronze retainers are used. In starting up the test, three grams of thetest grease are charged to the test bearing and worked into and aroundthe races and balls. The bearing is next rotated both clockwise andcounterclockwise for one minute each at 200 R. P. M. and assembled intothe test unit. The heaters and the motor are then started and the testbearing brought up to the test temperature as rapidly as possible, whichrequires 1.0 to 1.25 hours, while the spindle is rotated at a speed of10,000 R. P. M. After 24 hours of operation the heaters and motors areshut off for 2 hours, during which the temperature of the test bearingdrops to a minimum of 120-130" F. The total hours of operation,excluding the two hour shut-down periods, to the failure point isrecorded as the hours to failure.

As shown by the data given in Table I, greases containing both sodium orlithium myristate and indigo as thickening agents ran for several timesas long in the high temperature performance test at 350 F. as did thegreases thickened with either sodium myristate or indigo alone, showingthat a pronounced synergistic effect is obtained upon the hightemperature properties of a grease by the use of these two materials incombination as thickening agents. The unexpected nature of this effectis shown by the fact that the use of sodium myristate in combinationwith carbon black only produced a grease which was inferior to thegrease thickened with carbon black alone.

In addition to their very outstanding high temperature performanceproperties as discussedabove, the greases prepared from indigo-soapmixtures in accordance with this invention had superior lubricatingproperties at low temperatures also, grease No. 2, for example, which isrepresentative of a preferred embodiment of the inven-' tion, havingappreciably lower low temperature, torques at temperatures down to F;than grease 'No. 5; wherein sodium myristate was employed as the solethickening agent.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made with-. out departing from thespirit-and scope thereof and therefore, only such limitations should beimposed as are inf dicated in the appended claims.

We claim:

1. A lubricating grease consisting essentially of an oleaginous liquidlubricating base thickened to a grease consistency with about 5 to 20percent by weight based on the weight of the composition of indigo infinely divided form and about 5 to 20 percent by weight based on theweight of the composition of a soap selected from the group consistingof sodium and lithium soaps of fatty acids containing from 12 to 16carbon atoms per molecule.

2. A lubricating grease according to claim 1 wherein the proportion ofindigo to the said soap is from about 1:2 to about 2:1 by weight.

3. A lubricating grease according to claim 1 wherein the said soap isselected from the group consisting of sodium and lithium myristates.

4. A lubricating grease according to claim 1 wherein the said oleaginousliquid lubriating base comprises about 20-100 percent of a highmolecular weight polyester of lubricating characteristics.

5. A lubricating grease according to claim 4 wherein the said polyesteris a product obtained by reacting a dibasic aliphatic acid with a glycoland a compound selected from the group consisting of monohydricaliphatic alcohols and mono-carboxylic aliphatic acids.

6. A lubricating grease according to claim 4 wherein the said polyesteris represented by the general formula wherein R is selected from thegroup consisting of aliphatic groups and aliphatic ether groupscontaining from 4 to 12 carbon atoms, R1 is an aliphatic groupcontaining from 1 to 12 carbon atoms, R2 is an aliphatic groupcontaining from 1 to 12 carbon atoms, and x is an integer from 1 to 5.

7. A lubricating grease according to claim 4 wherein the said polyesteris represented by the general formula wherein R is an aliphatic groupcontaining from 6 to 12 carbon atoms in branched chain arrangement, R1is an aliphatic group containing from 7 to 8 carbon atoms, R: is analiphatic group containing from 4 to 9 carbon atoms in branched chainarrangement and x is an integer from 1 to 2.

8. A lubricating grease according to claim 4 wherein the said polyesteris ditridecylazelate.

9. A lubricating grease consisting essentially of an oleaginous liquidlubricating base containing about 5-15 percent by weight of indigo infinely divided form, about 5-15 percent by weight of a soap selectedfrom the group consisting of sodium and lithium myristates, about 0.1-8percent of N,N' diphenyl para-phenylene diamine and about 03-15 percentby weight of tricresyl phosphate, said oleaginous liquid lubricatingbase comprising in minor proportion a mineral oil of lubricatingcharacteristics and in major proportion a high molecular weightpolyester of lubricating characteristics.

"7 10. A lubricating grease according to claim 9 wherein the saidpolyester is represented by the general formula wherein R is analiphatic group containing from 4 to 12 carbon atoms, R1 is an aliphaticgroup containing from 1 to 12 carbon atoms, R2 is an aliphatic groupcontaining from 1 to 12 carbon atoms, and x is an integer from 1 to 5.

11. A lubricating grease according to claim 10 wherein the saidpolyester is a compound having the formula 12. A lubricating greaseconsisting essentially of an oleaginous liquid lubricating basecontaining about 5-15 percent by weight of indigo in finely dividedform, about 5-15 percent by weight of sodium myristate, about 0.5-2

8 percent by weight of diphenyl-pararphenylene diarnine and about 1- -5percent by weight of tricresyl phosphate, said oleaginous liquidlubricating base comprising inminor proportion a mineral oilloflubricating characteristics and in major proportion a polyester oilcomprising essentially a compoundlof the formula(iso-CsHrO-OOC-(CI-Iz)a-COOiso-CaHre- OOC(CH2)sC0O(iso-CaH11) ReferencesCited in the file of this patent UNITED STATES PATENTS 2,542,570 Puryearet a1. Feb. 20, 1951 2,628,974 Sanderson Feb. 17, 1953 2,639,266Dilworth et a1. May 19, 1953 2,663,690 Eckert Dec. 22, 1953 2,663,691Dilworth Dec. 22, 1953 2,679,480 Brannen et al May 25, 1954

1. A LUBRICSTING GREASE CONSISTING ESSENTIALLY OF AN OLEAGINOUS LIQUIDLUBRICATING BASE THICKENED TO A GREASE CONSISTENCY WITH ABOUT 5 TO 20PERCENT BY WEIGHT BASED ON THE WEIGHT OF THE COMPOSITION OF INDIGO INFINELY DIVIDED FORM AND ABOUT 5 TO 20 PERCENT BY WEIGHT BASED ON THEWEIGHT OF THE COMPOSITION OF A SOAP SELECTED FROM THE GROUP CONSISTINGOF SODIUM AND LITHIUM SOAPS OF FATTY ACIDS CONTAINING FROM 12 TO 16CARBON ATOMS PER MOLECULE.